Running Struggles (advice welcome)

I did my first marathon last December and my first half-Ironman earlier this year (Galveston). My run times have been coming down consistently until recently and I can't quite figure out what is going on. I seem to be backsliding....

I had a flair up of tendinitis in my Achilles and took 2 full weeks off of running and focused on the bike and swim for those weeks. I eased back into running despite some tightness in the ankle and continued taking it easy and avoid speed workouts and hills as they aggrevated it more. I focused hard on cycling and picked up my strength training even more.

My Achilles is getting better now, still tight but improving, and my runs just feel terrible. I have my volume back up to 25-30 miles/week and have for a few weeks and there was never any real dip in training, just a refocusing for awhile while the Achilles healed some. From a perceived effort level, I have to drop a full minute/mile to feel the way I did before the Achilles issue started. Texas heat and humidity is in full effect and I'm sure it has some effect, but not this much. I feel like I'm losing ground on the run despite a lot of hard work and any advice is greatly appreciated.

Few additional details:
Diet hasn't changed in any significant way
Sleep patterns have been very similar
Training time per week has stayed stable with some refocusing on cycling and strength training for awhile

Thanks in advance for any help/advice!