Add SPF record for multiple systems in different servers

I have a domain with a published SPF record (v=spf1 a mx ip4:xx.xxx.xxx.25 ~all) for it (e.g: xyz.com)
also this domain has four subdomains:
sub1.xyz.com xx.xxx.xxx.29
sub2.xyz.com xx.xxx.xxx.30
sub3.xyz.com xx.xxx.xxx.31
sub4.xyz.com xx.xxx.xxx.32
and every one of those subs in a different server and different IP, when sending emails from subdomains (let's say for example [email protected]) the SPF check fails, in this situation should I publish individual SPF for every subdomain or include them in the main SPF record? and if I am supposed to include in the main, this must be done in a mechanism:

"v=spf1 a mx a:sub1.xyz.com a:sub2.xyz.com a:sub3.xyz.com a:sub4.xyz.com ip4:xx.xxx.xxx.25 ~all"

or
include mechanism:

"v=spf1 mx a ip4:xx.xxx.xxx.25 include:sub1.xyz.com include:sub2.xyz.com include:sub3.xyz.com include:sub4.xyz.com ~all"

or
mx mechanism:

"v=spf1 a mx mx:sub1.xyz.com mx:sub2.xyz.com mx:sub3.xyz.com mx:sub4.xyz.com ip4:xx.xxx.xxx.25 ~all "

Solution 1:

If the email is actually coming from the subdomain, that subdomain needs its own independent SPF record.