It looks like this is missing an additional composition credit: 
Yasuhiko Takashiba (as TAKASHIBA)
From the staff roll:

picture from 
MAMEND
On the 
original 1993 OST, they only received a "special thanks":
 
But they were credited as one of three composers on the 
Arcade Disc In JALECO -VARIETY- in 2013:

(Soldam is the third game on CD 3)
It's possible that the entry in the booklet might explain things, but I can't read Japanese...
 
(all scans from VGMdb)
Later this month, there will be an 
all Soldam album, featuring music from the original, the GB conversion, an unreleased Famicom conversion and the new Switch game 
Soldam: Bloom Declaration. Maybe the booklet from that will clear things up a bit.
(
City Connection, who is behind both the Jaleco compilation album and the game, owns the rights to Jaleco's IPs since 2013)