Extremely faint image on negatives but no text in rebates

Hey everyone. I'm developing 400 ISO HP5. All my negs (two tries) have resulted in faint images. The numbers that tell you the film brand and ISO rating and such don't show up on the film strip's rebate.

I use a recipe of:

I don't think it's my recipe or my dev time because the film name would develop in the rebate along with the faint images wouldn't it? I'm thinking it might be a light leak in my changing bag.

Can anyone help me out?

Two things I suspect. A recipe on the weak side, and developed a bit short. The recipe I use is metric, so won't translate well, but if it at all helps please do try it out. And my first effort with HP5 got developed for 13 minutes and turned out nicely. Could have done with a couple more minutes maybe. See group pictures (the pano).

My recipe and method:
Sodium carbonate (anhydrous): 40g/l
Ascorbic acid (pure vit-C): 16g/l
Instant Coffee: 40g/l
And for ISO 400 speed films a dash of Potassium Bromide:1-1.5g/l

Presoak in water at 68F, 4-5minutes
Pour out, then add developer and agitate 12-15 inversions initially, then 3 every minute. Pour out, water stop for one minute (fill and empty 5-6 times). Fix and wash as normal.

Good luck