Any requirements for producing blocks once Active?

Testnet validators on 26th and 27th positions are active for couple of days, but didn’t propose any blocks.
Are there any extra requirements for validators to start proposing blocks (like being in top 25 or 50), or everything is fine which means they’re in healthy state and awaiting for new transactions?
In comparison, SanSalvador in on 25th had 57 blocks proposed (1 every few hours).