A "bulk lot of five" refers to five of the same item.
Because of the use of "it's" in "It's had it", it refers to only one of the items. We don't know the situation for the other four.
Interested in Language
have had it
Be in a very poor condition; be beyond repair or past its best:
Yeah it's had it. I purchased a bulk lot of 5, with the seller saying he had not tried them and would not replace them if they did not work.
Do I correctly understand the parts in bold:
"A bulk lot of five (items of something) which all have broken down after I bought them"?