If that is a Purina Label - the date would be March 5, 2019 when it was milled/bagged.
It should be o.k. - does it smell o.k.?
Are they avoiding the heat at all? I would watch to see if they are overheating.
See that everyone is eating/drinking well.
Chicks can have an overload of Coccidiosis even while on medicated feed and while being in a brooder. Coccidia is found in poop and soil, is flourished in warm moist environments - a brooder is actually ideal for Coccidia especially around water stations that may have spilled, in water stations where chicks poop in them - yep, chicks do poop in water, it happens. If they are on medicated feed, only clean up damp spots - read your tag - they need to be exposed to their poop. Yes, this means that chicks will probably eat/taste a little poop - that is how Coccidia is spread - ingestion of the oocysts. Purina medicated chick starter contains a very low amount of Amprolium/Amprol - the same ingredient as Corid - this acts as a Thiamine (B1) blocker/mimicker which starves out Coccidia allowing the chicks to build resistance. Sometimes it's not enough if the chicks encounter a large number of oocysts in their environment.
All that said --- I would tinker with/adjust that temperature to make sure the chicks are not overheating. If you lose more, then I would get some Corid and use it.