It’s not as simple as they got wet from the sprinklers; it’s that they weren’t able to dry out (as indicated by the residual caulking I see). What was covering that area that’s since been removed? Other factors to consider include the type of lumber used and whether or not it was pressure treated lumber specifically designed for ground contact and/or whether or not the cut ends were treated.

you are right all these rotted area were underneath the wood panel/trim. we just removed them today. I am not sure how to find out weather the lumber was treated or not.

Busting out floor isn't nrccassary if post are resting on concrete now. The steel anchors are poured into slab now,re-use them. Complete replacement would be far less labor than pouring all those supports.

I was going to say exactly the same thing Klem did. And those posts are not treated wood. They look like they were installed well, the steel plate beneath is a good thing to keep the wood directly off the concrete.

Chahal, please do keep us up-to-date on how this is repaired. I'm sorry that you have to deal with it but, as a by standing rubber-necker, this is interesting. I would like to know all the possible solutions and how you decide to resolve the problem.

And soak the cut ends of the replacement post in a paintable wood preservative before installing. Preservative in a bucket, stand the post in the bucket and leave it a couple of hours/ overnight... Will take some engineering to keep the post in the bucket and to keep the bucket from tipping over. Better ideas?? (Maybe use baling wire or rope to anchor the new posts to the old posts to keep new post/ bucket from toppling over...?

Everything's easy on the internet. The reality is those footings wouldn't pass current code. Upgrading them in conjunction with post repair/replacement might be required by your inspector. Raising the posts off the ground is never a bad idea either.