My HT change was amazing and the new hair stayed strong for like 2 years. Then it got brittle and started falling out from overusing 2% Nizoral, it was a slow gradual progress.
I had to use the shampoo because of issues with seborrheic dermatitis (dandruff), and since the gentler Dr. Lee's regrowth shampoo was no longer available after they closed him down.
Stopped the shampoo and washed less frequently. My hair got stronger but then I was plagued with dandruff and how to remove it.
I finally found a decent shampoo with salicylic acid that keeps most of the thick dandruff away.
I also quit propecia, which I think did not do anything to improve my frontal new hair.
I am planning to have a second procedure to touch up my hairline now, so not 100% back to normal.
Remember the hair cycle is around 3 months, see if the lost hair grows back, but of course contact your Dr. and HT physician ASAP.