I think I replied to you about this issue on the other bulletin board. Does this quote sound familiar?
>>Martins don't start incubating when the first egg is laid. Like most birds, incubation is postponed till all or most of the eggs are laid, so that the nestlings will all hatch about the same time.
You count incubation from the day the
penultimate that is, the next-to-last, egg is laid. In your case, if the first egg was laid May 25, the 5th egg was laid May 29, so the next-to-last egg was May 28. Fifteen days from that date would be June 12, the earliest date you could expect hatching. Bad weather can delay hatching by up to 10 days, which takes you to June 22.
Before you give up on this clutch completely, I would wait a few more days.<<
Anyway, congratulations on your successful hatching. Isn't it exciting? Doing nest checks throughout the nestling phase is a really good idea. Not only can you monitor what is going on with your fledgling colony, but it is TOO much fun to watch the babies grow.

Every 3 to 5 days is recommended, but with small, new colonies, you can check every day if you like.

Many people recommend doing nest changes at 10 and 20 days incubation to minimize nest parasite problems. Just remember to
stop nest checks after the babies reach 20 days old, to avoid causing premature fledging.