Did you take spot readings of the shadows? If they were more than about 3 stops below the gray card, you will have lost the detail.(posted 9888 days ago)Kodak say, on reciprocity failure, that 10 seconds should be increased to 15s, and 100s increased to 200s (for T-Max 100).
So your 5 minutes (300s) should have been increased to something more than 600s (10 minutes).
On development, they suggest 6 min in T-Max at 24 deg C. You say you normally use 5 min.
Increasing development by about 40% will raise the film speed by about 1 stop, but will also increase contrast. You might try using a more dilute developer to reduce the contrast, which will also require greater development times. 1+9 for 22 minutes at 24 deg C might be a good starting point.
If these pictures are important to you, you should do tests first. Simulate the original subject (eg with gray and white paper), shoot it, and develop. Examine the negatives for shadow detail. Adjust as necessary. When happy, develop your original roll.