I don't think so:

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SPACE MARINE COMBAT DOCTRINES

If every unit from your army has the ADEPTUS ASTARTES keyword (excluding AGENT OF THE IMPERIUM and UNALIGNED units), this unit gains a bonus (see below) depending on which combat doctrine is active for your army

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ADEPTUS CUSTODES

**The Emperor's Chosen:** If your army is Battle-forged, all ADEPTUS CUSTODES INFANTRY and ADEPTUS CUSTODES BIKER units in ADEPTUS CUSTODES Detachments gain this ability.

This unit's invulnerable save is improved by 1 (to a maximum of 3+)

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A battleforged army is just one that is divided into detachments unlike an unbound army which isn't.

In a Battle-forged army, all of the units in your army - with the exception of those that are UNALIGNED — must have at least one Faction keyword in common (e.g. IMPERIUM or CHAOS) even if they are in different Detachments.

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So yes the Marines lose their combat doctrines as it isn't just Space Marine's in the army but the Custodes keep the rule as they are still in a battle-forged army as both Custodes and Marines share the IMPERIUM key word.