Triathlon to just Running

That's indeed 'pro-caliber' training if you're not BSing and actually doing that much training. Well over 20 hours per week. 

I'm curious to see what your current training regimen as a pure runner is, if you were indeed running 70-80mpw as a triathlete (which is more than most pros run per week in training.)

If that training load is on the level, then guessing burnout and/or overtraining. That's a long season of training with what sounds like little or no down time. Wondering if your legs losing defintion and strength could be due to weight loss (breaking down muscle), possibly from inadequate nutrition for the volume of training you were doing. The dramatic loss of energy would also make me wonder about anemia, mono, or other medical issues. A healthy young person with a great training base shouldn't be feeling that awful! Or are there other stresses in your life that are sapping your energy? That volume of training and running ought to make you a strong runner with a great base. At most, when switching to run-only training, there might be an adaptation period where you get used to doing more focused tempo and speedwork. But the issues shouldn't be that dramatic. I would look at general health, nutrition, recovery, and the need for a break!

You need to provide more info. How old are you, how long have you kept that level of training. Do you have any other symptoms, sleep quality, appetite, weight trends.. How long has this degradation in performance been going on....

First signs of overreaching are loss of performance. Overtraining escalates from there. 

I came across a staggering statistical info some time back, 90% of high school or college xcountry and track runners end up injured at some point. Cannot remember where I found that, but sure will never forget. It just tells you how oblivious some of those coaches are. 70-100mi/week at that level is quite normal, but just kills them at one point or another. Much like in parts of swimming community where you have select programs around the country drive their swimmers at 90k/week over and over, give them a little pre race rest, cross their fingers, hoping that the fittest will come back from a hole and they call it a taper.

Unfortunately, our OP is from that school and nobody told him that 70mi a week of running with a triathlon program is not an option.  

Thanks for your advice everyone.

Burnout has definitely crossed my mind.

But to answer a few of your questions... I'm 19 years old. My tri training lasted about 3 months. I did not lose much weight, if any. My diet became more limited when I went off to school. I was expecting 70 mpw to be even easier if I could do it on top of swimming and biking, but it wasn't the case.

My weight training consisted of mainly squats, hamstring curls, and calf raises..with a light upper body routine as well.

As soon as I got to school, things began to go down hill and the season just was ugly.

IF burnout or illness is not the case, I was thinking of hopping back on the bike again and see how that works out.

It's one or the other....at 19 you were working out harder than a lot of pros (my guess is without the base they have obtained over the years)

I am not a fitness expert, but let me take an angle that hasn't come up yet, just to get the room thinking.

Since you are back in school at 19 sounds like you might have just started college, or gone back for your sophmore year.  College has been known to be too stresfull, or too relaxing.

Are you getting enough sleep?  Are you staying up all night studying?  Are you staying up all night partying?

Inotherwords, what else is different in your life OTHER than the number of workouts you are doing.

As for my lifestyle, its been quite an adjustment so I have really tried to focus on things like healthy diet and sleep.

I am definitely considering getting some blood work done by the doctors at school.  I feel fine though doing everything but running.

It has been weird though because one day I felt amazing and was keeping up with the best guys on the team during 1k repeats.  Then the next day I feel terrible again (other than the fact that I just had a workout the day before).

The only thing I would say I did differently are hamstring push ups using an exercise ball the day before that workout.  After doing these exercises it seemed I had all my leg power back and turnover again.  Which is my reasoning toward having weak hamstrings.  I have been reading articles on how the quads can overpower the hamstrings in runners, and are finding them somewhat relevant.

Now when I am running it is difficult to bring my knees up as my foot wants to hit the ground right away, and bringing my heel up to stride again is very difficult.  Is there anyway it could be some mechanical issue?

Thanks again for all your advice.  I really appreciate it. 

I agree with your reasoning although this routine has treated me well for quite some time.  I found that the squats done nothing but helped my leg endurance, and my hill running ability had improved dramatically.

Are there negatives sides to this type of lifitng?

Yep...HS XC has the highest injury rate of all HS sports.  Keeping my runners healthy is the most important thing to me as a HS coach.  

Make sure you get your iron count checked out.